Discrimination between poultry eggs on the basis of some observable quality is a well-known and long-used practice in the poultry industry. "Candling" is a common name for one such technique, a term which has its roots in the original practice of inspecting an egg using the light from a candle. As is known to those familiar with poultry eggs, although egg shells appear opaque under most lighting conditions, they are in reality somewhat translucent, and when placed in front of a direct light, such as a candle or light bulb, the contents of the egg can be observed to a certain extent.
In most such practices, the purpose of inspecting eggs, particularly "table eggs" intended for human consumption, is to identify and then segregate those eggs which have a significant quantity of blood present, such eggs themselves sometimes being referred to as "bloods" or "blood eggs." These eggs are less than desirable from a consumer standpoint, making removal of them from any given group of eggs economically desirable.
Eggs which are to be hatched to live poultry also may be candled midway through embryonic development or later to identify infertile ("clear") eggs and remove them from incubation to thereby increase available incubator space. Such inspection and removal is particularly useful in turkey hatcheries. Candlers also attempt to identify and remove "rotten" and other dead eggs on the basis of their internal color. Such techniques are difficult and unreliable, however, so that many rotten eggs are inadvertently returned to incubation.
As stated above, early techniques for identifying such eggs comprised simply inspecting the egg in front of a candle and discriminating on the basis of the appearance of the contents. Later inspection techniques used artificial light sources, and in recent years, spectrographic techniques have been developed which irradiate eggs with particular frequencies of light which are sensitive to the presence of one or more of the characteristic components of blood (e.g. hemoglobin) to make a more accurate determination of whether or not the contents of the egg are indeed filled with blood or whether some other factor is interfering with the egg's appearance or quality.
Still other techniques inspect table eggs for the purpose of determining whether or not they are cracked. These techniques also use light sources and detectors because cracked eggs will often transmit more incident light towards a detector than will intact ones.
Recently, however, there have developed other reasons for distinguishing between eggs. One of these reasons is the advancements in techniques for treating poultry embryos with medications, nutrients, hormones or other beneficial substances while the embryos are still in the egg. Such techniques are quite advantageous compared to treatment of newly born chicks which often must be medicated, for example, by being hand inoculated one by one.
In embryo treatment techniques, the purpose of discrimination between eggs is to determine whether or not the eggs are alive or dead and whether they should consequently be treated with the particular vaccine, nutrient, hormone or other material under consideration. Accordingly, the decision of whether or not to treat the egg involves greater expense than simply the cost of the egg, including the cost of the dosage of the injected material, the cost of operating any given injection system and the cost of further incubation. Additionally, infertile or early dead eggs foster bacterial growth and thus are frequently infected. An embryo injection system which penetrates an infected egg risks contaminating live eggs which are subsequently injected by the system.
Finally, although the typical tests for appearance and blood can discriminate to some extent between fertile and infertile eggs, there are no reliable automatic methods for distinguishing between live and dead eggs. Therefore, the embryonic treatment industry is in economic need of a highly reliable method of discrimination of live eggs from dead ones and particularly for the detection of infected or rotten eggs.
Of course, any technique for discriminating between live and dead eggs must be either noninvasive, or so minimally invasive, that the live eggs will not be harmed by the discrimination technique.
Accordingly, it is an object of the present invention to provide a noninvasive method of, and apparatus for, distinguishing between live and dead poultry eggs on the basis of their individual monitored temperatures.